Battle plan: Dr Thomas Tsang and Prof Gabriel Leung brief reporters on the city's human swine flu prevention work.

Five more imported human swine flu cases have been confirmed, involving two men and three women who flew in from abroad, taking the total to 20.

The city's 16th confirmed case involves a 21-year-old woman who arrived from Los Angeles at about 7am on May 28 on flight CX881. She returned to her home on a public bus. She developed symptoms at home and called the Centre for Health Protection's hotline. She was sent to Princess Margaret Hospital by ambulance.

Another 21-year-old woman flew in from San Francisco on flight SQ1 at 6am today. She felt ill on the plane and port health officers at the airport sent her to Tuen Mun Hospital.

The 18th swine flu patient is a 21-year-old man who flew in from New York via Seoul and arrived at 8pm on May 26. He did not have any symptoms while on flight KE607. He fell ill May 28 and took a taxi to North District Hospital.

The 19th and 20th cases involve a 24-year-old man and a 19-year-old woman who arrived from New York on flight CO099 at 8pm May 27.

Centre Controller Dr Thomas Tsang said the centre will trace patients' family members and close contacts, as well as passengers who had been on the same flights.

Mitigation measures

Under Secretary for Food & Health Prof Gabriel Leung said the steering committee to stem the virus' spread has approved the arrangements and measures to tackle the situation during the early mitigation phase.

When the first local case emerges in Hong Kong, the mechanism for the mitigation phase will be activated and primary schools, kindergartens, nurseries and pre-schools will suspend classes for 14 days.

During the middle of the suspension period, the Government will decide whether classes can resume. If the suspension period is long, all school examinations except those for primary five students will be cancelled.

Special arrangements will be made for primary five students so they can go back to schools at a designated time to take exams. The Government may also consider cancelling the Territory-wide System Assessment if the suspension period is long.

Designated clinics

The Hospital Authority's seven designated clinics will be activated and the number of clinics will increase to 18 if there are many people seeking help.

During the mitigation phase the Government will no longer trace patients' social contacts but their close contacts will be given Tamiflu and put under medical surveillance. If community outbreaks are severe, the Government will consider reserving the drug for patients only.

All passengers arriving in Hong Kong will need to complete a new health declaration form from June 1. The form requires travellers to fill in more information, including their seat number on the flight, ship or vehicle, their destinations for the next seven days after arriving in Hong Kong, and the transport to be used and contacts for those seven days.